530 likes | 771 Views
Butterflies and Host Plants. Is it a Family Affair?. Kenneth A. Bridle, Ph. D. Director of Stewardship and Inventory Piedmont Land Conservancy August 2012. This Presentation . My discomfort with Host Plant Lists Most are over simplifications Even if lists are correct, Why?
E N D
Butterflies and Host Plants Is it a Family Affair? Kenneth A. Bridle, Ph. D. Director of Stewardship and Inventory Piedmont Land Conservancy August 2012
This Presentation • My discomfort with Host Plant Lists • Most are over simplifications • Even if lists are correct, Why? • My interest in Plant and Insect Interactions • Co-evolution? • My interest in Natural Product Chemistry • Chemical ecology and environmental impact
Butterfly Host Preferences Vary • Some Butterflies use many kinds of plants: • Painted Lady, Mourning Cloak, Red-spotted Purple • Gray Hairstreak, Spring Azure • Some Plants support many kinds of Butterfly: • Willow, Cherry, Nettles, Grasses, Legumes • Some Butterflies and Host Plants are very specific • Monarchs, Pine elfin
How Do Butterflies Recognize their Host Plants? • Some evidence suggests that some butterflies can learn the leaf shape/texture • Some insects, including butterflies might be able to see distinctions in leaf color not obvious to us • UV light patterns similar to flowers and bees • The best evidence seems to be chemical selection
The history of insects eating plants (greatly abbreviated) • The first insects were polyphagus (Paleozoic) • They ate any plant material they found • (sucking sap comes first then chewing later) • Most plant matter was similar in composition • Later, some insects specialized in eating spores • Plant spores are higher in nutrient value than other tissues • Some spore eaters later moved to pollen with the rise of the angiosperms (Cretaceous) • This avoids much toxic chemistry • Pollen is hard to digest • Finally some pollen eaters switched to nectar. • Insects with complex life cycles often specialize in different foods at different stages
Evolution from Polyphagus to Oligophagus to Monophagus • Suppose all insects started out as food generalists • Competition among plant eaters is high • Impact on plants by all the eaters is high • Plants develop some protective chemistry to defend themselves • An “arms race” starts as insects develop ways to avoid or metabolically adapt to these new chemistries. • What were once toxic chemistries, soon became markers, attractants and nutritional requirements. • So what started as chemical defense became the basis of mutual adaptation.
Plant Chemicals influence Insects in many ways • Repellants / Attractants • Change movement direction of insects • Start or Stop Movement • Simulant or depressant of locomotors systems • May work in-vitro • Start or Stop Feeding • Antibiotics • Limit larval growth and development • Limit life expectancy/ fecundity of Adults • Ovipositional cues
Types of Plant Chemistry • Basic Biological Chemistry • Carbohydrates, Proteins, Nucleic Acids • Plant Structural Chemistry • Cellulose , Lignin, Tannin • Plant Secondary Natural Products • Not strictly necessary for growth and development • Internal toxic compounds • Volatile organics that surround the plant • Leaf Surface Chemistry • Induced or Constitutive • Induced are made in response to damage
Gas Chromatograph of Leaf Surface Chemistry, Nightshade and Tomato
Plant Chemistry is a Family Trait • Closely related plants share growth habit, structural and biochemical themes • They look (and smell) alike to us and insects • Chemistries that have adaptive advantage are continued from ancestral types of plants • If it works stick with it • Members of plant families usually have variations on the basic chemical theme(s) • Tweaking and improving all the time
What are the important butterfly host plant families in our area? • Started with the list of common plant families, identify the ones known to be used by butterflies • 35 families host butterflies out of about 150 in flora • About 17 plant families host the majority of butterflies • Made a table of these most common host plants compared to the families of butterflies • XX means many butterflies in that group
Butterfly Family Groups • Swallowtails • Tigers, Pipevines, Blacks, Zebra • Blues and Hairstreaks • Azures, Eastern-tailed Blue • Brushfoots • Monarch, Fritillaries, Buckeye, Satyr, Wood nymph • Yellows and Whites • Cabbage White, Sleepy Orange, Sulfurs • Skippers • Fiery, Silver Spotted, Sachem
Thoughts on Family Correlation • At the Family level there appears to be a segregation of butterfly families using plant families • No one plant family is used by all butterflies • Three plant families are used by three butterfly families • Three plant families are used by two butterfly families • Eleven plant families are used by only one butterfly family • Many families are not butterfly hosts, but may be hosts of other insects.
The Whites and Yellows group nicely in two families • Yellows use legumes, Whites use brassicas • Skippers group into three plant families • These are most often found in open fields and grassland natural communities. • The Swallowtails and Brushfoots seem to diversify most • Swallowtails predominantly on woody species • Brushfoots seem to favor herbaceous • If the Gossamers, Yellows and Whites and Skippers were broken into subfamilies other patterns might appear • This is by no means a rigorous scientific study, there is lots of room for improvement.
Additional Information • Subsequent to the original presentation, “Butterflies of the East Coast an Observers Guide” was published (Cech and Tudor, 2005) • These authors recognize the importance of plant families to the butterfly host plant discussion in several parts of this book. • They also integrate host plant use with theories of butterfly lifestyle or success strategies
Host-Plant Related Lifestyles Cech and Tudor 2005
Final thoughts • Host plant selection and use is complex and is certainly varies depending on the species involved • Ovipositional cues are most likely chemical although some visual cues and random trial also occur • Chemical content of the leaf both feeds larva and may protect larva and later adults from predation and completion. • These insects are often harmed or suppressed, but they are still successful. • Relationships of host plants and insect predators reflect past evolution and speciation. • Plant chemical arms race might be responsible for insect diversity explosion in Cretaceous • Diversity of plant families in an area probably supports a diversity of butterfly species • Good for wildlife sensitive gardeners to know • Awareness of chemical cues in nature will make us better naturalists.
Thanks to: • Dennis Burnette • Founder of the Carolina Butterfly Society • Motivational force behind the Triad Chapter • And special thanks for any butterfly images which may have slipped into any of my butterfly presentations! • To all the folks who organize and report butterfly counts. This is really great citizen science. • To the current board of CBS and organizers of this meeting.